The invention relates to an electrical noise filter, which consists of a filter housing and associated electrical components. The filter includes, in particular, inductances and capacitances, installed in the housing and embedded in a sealing compound, and with electrical connections, in particular flat plugs, litz wires, pin plugs and the like, which protrude out of the filter housing at open face ends and which are connected to electrical circuit components.
Noise filter of the above mentioned kind are intended for use in desk computers, office machines and medical equipment and the like. Their principal function is the reduction of the line related noise levels. Since these filters, due to their application, are subjected to high electrical and magnetic field strength levels because of the environment in which they operate, it must be ensured that their suppression effectiveness is not reduced through unintended coupling of electrical and magnetic interferences to the wiring or the components of the filter circuit. Especially when used in electrical equipment with combined power supplies and/or microprocessor systems which have long bus runs, these problems are encountered frequently. Tests can be conducted to solve these problems and they involve, for example, the use of metal housings for the noise filters, closed on all sides and with insulated leadthroughs for the terminals. The metal housings can be deep-drawn nickel silver housings or two-piece sheet iron housings soldered tight.
Such filters have become known, for example, as filters with integrated cold appliance plugs in which the connections from the net side are made via this cold appliance plug--usually a so-called power outlet--and the contact to the equipment to be provided with the filter via flat plugs, litz wires, soldering lugs or the like. In this connection, reference is made, for example, to the Technical Report from the Components Area, Ordering No. B/24 18, published by Siemens under the title "Electromagnetic Compatibility Through the Use of Noise Filters", in particular page 18, and to the Siemens brochure "Radio Noise Filter", available under the Ordering No. B/22 84, Supply Program 1980/81, pages 12 and 13.
The terminals and the carriers of the electrical components are tightly cemented into a halfround cup of nickel silver sheet. In this noise filter, the electrical components per se are mounted, insulated and manually soldered into the halfround cup. Subsequently, the electrical components are fixed with a soft epoxy resin compound from the open side of the halfround cup and then mechanically protected by a hard sealing compound.
Other commercially available noise filters employ a deep-drawn nickel silver housing in place of the halfround nickel silver cup. The components are then mounted and soldered in an auxiliary frame with flat plugs. Cementing the components and flat plug parts located in the filter housing is accomplished through a hole in the nickel silver housing which must be tightly sealed to plugs and frame by adding sealing rings. The cementing hole is covered up by a glued-on name plate.
Other noise filters also available commercially utilize a soldered jacket tube of tin plate, the electrical components being mounted to a base plate which is subsequently riveted to the plug. The ground connection is soldered on through a hole in the jacket tube which must be pushed over the plug first. The soldering point is covered up by a name plate. The electrical components are cemented in from the open backside of the jacket tube.